At each centre, all patients with DCIS referred to radiation oncology will be documented. When a physician identifies an eligible patient, the patient will be approached by the referring physician or delegate to voluntarily provide informed consent to participate in this study. Consenting patients will be registered through the Ontario Clinical Oncology Group's (OCOG) web-based registration system. Data related to the patient demographics, surgery details, and tumour characteristics will be collected. The preliminary treatment recommendation and patient preference for treatment will be documented. Patient Decisional Conflict will be documented by the patient using the Decisional Conflict Scale (DCS). The patient's tumour specimen will be sent for analysis to Genomic Health. DCIS score results will be sent to the referring physician. OCOG will also receive the DCIS score results. The final treatment recommendation, patient preference, and treatment received by the patient will be documented. Patient decisional conflict will be documented by the patient using the DCS. The study data will be verified by source documentation.